Een duizend only make sense in specific contexts in Dutch. E.g. Er was een duizend man = There were at about a thousand people, or Heb je een/één duizendje? = Do you have a/one banknote of a thousand?. In the former sentence it can only mean een as it's an estimation, in the latter it can be either een or één, depending on what is meant.

In normal counting duizend is never preceded by een. The same goes for honderd, tienduizend and honderdduizend. But for bigger numbers it is used: een miljoen (a million), een miljard (a billion), een biljoen (a trillion). Because the context and meaning are clear, no accents need to be added to een. For any number above a million, keep in mind the long scale is used in Dutch, whereas most English speaking countries use the short scale: https://en.wikipedia.org/wiki/Long_and_short_scales

Technically, the subject can be stressed. We just don't know the context. So for now, you can choose between the two, they're both correct. Unless it's a listening exercise, than the one you hear is correct.

In English, thousand normally takes the article: almost a thousand people, about a thousand people; whereas in Dutch, duizend does not normally take the article: bijna duizend mensen, ongeveer duizend mensen. See explanations above.